C_(b) exhibits two π bonds: one to C_(a), and the other to C_(c). Imagine a picture of C_(a), C_(b), and the two different p orbitals that C_(b) is utilizing to form its two π bonds. (It may be helpful to also consider the p orbitals on C_(a) and C_(c) that are being used by each of those atoms. orbitals on C_(a) and C_(c).
Ch exhibits two π bonds: one to Ca, and the other to Cc. Imagine a picture of Ca, Cb, and the two different p orbitals that Cb is utilizing to form its two π bonds. (It may be helpful to also consider the p orbitals on Ca and Cc that are being used by each of those atoms. D orbitals on C and Cc.